In warehouse inventory control, it is known to use handheld wireless units communicating with a central computer through one or more base stations. The central computer is typically provided in a wired Local Area Network (LAN). The base stations handle data traffic between the central computer and the handheld wireless units. Each base station is provided with a radio through which data received from the central computer is transmitted to the handheld wireless units, and vice versa.
The wired LAN uses a wired network protocol, such as Transmission Control Protocol/Internet Protocol (TCP/IP) for communications between wired communication devices. Wireless networks have much lower capacity and higher error-rate compared to wired networks. The common wired protocols are very inefficient and often not suitable for wireless networks. Thus, the wireless devices use a wireless network protocol which is designed for use over a wireless network.
A typical base station monitors messages on the wired network. When the base station recognizes that a message on the wired network is intended for one of the wireless handheld units, it strips all of the wired network protocol information from the message and replaces it with wireless network protocol information. For this reason, a base station is sometimes called a protocol converter.
There exist base stations for connecting a wired network and wireless devices, such as those connecting cellular phones and public telephone systems. However, these base stations are very complicate and costly to manufacture. Accordingly, they are generally not suitable for warehouse inventory control.
In order to connect two networks, it is known to use bridges and routers. A bridge connects two networks which use the same protocols. The bridge reads data received in its input. It creates a table of end-stations indicating the direction of the connection of the end stations. The bridge forwards the data as appropriate. However, it does not deal with connections between two networks which use different protocols. Further, existing bridges are designed for connecting two wired networks. A router can act as a protocol convertor. It alters packets to connect two networks which use different protocols. However, existing routers are generally designed for connecting two wired networks.
U.S. Pat. No. 5,546,397 issued to Mahany on Aug. 13, 1996 discloses an access point which is a base station provided on a wireless local area network with which roaming portable or mobile computer devices can connect and communicate. Each access point uses two wireless adapters and a low level protocol processor. The second adapter is essentially a backup in the event that the first adapter fails, thus improving the reliability of the access point and the entire network. Otherwise, the access point of Mahany functions in the same way as a typical base station described above, and does not provide any other additional functionality.
Therefore, it is desirable to provide an apparatus which can bridge a wired network and a plurality of wireless devices of different types or modalities, without performing protocol conversion, and which is simple and suitable for warehouse inventory control.